be set aside as a wildlife habitat and to protect the fishery. In 1963, Pacific Power and Light Company donated the Rise and the seven acres surrounding it to the city of Lander for use as a park. In 1970, city and state officials working with the state legislature and private citizens created Sinks Canyon State Park, the first park created under the newly formed Wyoming Recreation Commission. The bill creating the park was signed in 1971. A new overlook was built at the Rise in 1972; the visitor center was completed in 1973. Natural history Geology The Madison Limestone Formation was carved by glacial movement, leaving extensive underground fissures and steep cliff walls. The gradual recession of the ice left glacial moraines along the canyon floor. The canyon is the second most southerly of the many canyons along the eastern slope of the Wind River Range. The Rise The exact route of the passage is unknown, and dye tests have shown that the water takes over 2 hours to make its 1/4-mile underground journey. Additionally, more water flows from the Rise than enters the cavern at the Sink. The Crow Indian name of the river, "Popo Agie" (pronounced po-PO-shuh), is taken to mean "gurgling river." Plant life The canyon has a wide variety of plant species which differ depending on elevation and location. Numerous types of grass, trees, shrubs and other species of plants grow throughout the canyon. The canyon's area is generally divided into two main ecological zones: a subarid environment that is mainly populated by sagebrush and a pine-fir montane forest zone. Trees The timberline in the region is roughly between 7,217 and 8,530 feet above sea level. Most trees in the canyon grow on the north-facing wall, and the concentration of different species depends on the different ecological zones within the canyon. Common tree species include aspen, subalpine fir, Douglas fir, lodgepole pine, Engelmann spruce, and whitebark pine. Trees growing within the canyon can live for hundreds of years. Studies of tree rings conducted on Douglas fir in the canyon have found trees which started growing as early as 1649, though some of the trees were deceased at the time of sampling. Wildlife Wildlife, including prairie rattlesnakes, bull snakes, mule deer, and yellow-bellied marmots, is diverse and abundant in the area. Some 94 species of birds have been observed within the canyon including golden eagles and